1. Field of the Invention
The present invention relates to a d.c. high voltage supply, particularly for an X-ray emitter tube. However, it can also apply to other fields. The supplies in question are intended to be connected to a general electric mains.
2. Description of the Prior Art
Most of the supplies have high frequency generators at present. The mains undergoes rectification and filtration, the d.c. voltage obtained is rippled at high frequency by a ripple generator, the ripple voltage is raised by a step-up transformer, followed by rectification and filtration. This type of supply functions perfectly when the mains is of the three-phase type, but certain problems arise with the single-phase type. Thus, there is a voltage trough between two half-waves. Thus, in this trough, the ripple generator cannot take power from the mains. The use of a LC filter for storing energy at the peak of the sinusoid, so as to restore it during said trough cannot be used for power levels of approximately 30 to 100 kW. The filters become enormous as regards size and cost. Another standard solution consists of directly raising the single-phase mains voltage and then rectifying it after raising. However, the rectified high voltage follows the system and drops completely in the voltage troughs between half-waves. The spectrum of the X-rays emitted then extends over a vast range. This solution is increasingly falling into disfavour and is in fact forbidden in certain countries.